It would be easy for the Sporting Kansas City defense to give itself a hearty pat on the back after posting three shutouts in the season’s first four games.

Led by goalkeeper and captain Jimmy Nielsen, Sporting KC has only been scored on once.

That goal came on a free kick by FC Dallas’ Ricardo Villar from atop the penalty box, so Sporting KC’s opponents are still looking for the first goal during the run of play.

Powered by the stingy play from Nielsen and the back line — central defenders Matt Besler and Aurelien Collin with left back Seth Sinovic and right back Chance Myers — Sporting KC, 4-0-0, is off the best start in MLS this season and the best start in the club’s 17-year history.

But manager Peter Vermes warns against being too self-congratulatory.

“In some respects, we’ve been pretty good defensively, but we’ve also made some mistakes,” Vermes said. “We skirted a situation the other night with (Chivas USA’s Nick) LaBrocca. One of the biggest things that happens when you’ve had a few wins under your belt is that things get glossed over. We’ve made some mistakes. The difference is other teams haven’t capitalized on them.”

LaBrocca wriggled free in the penalty box and probably should have netted a goal, but his left-footed chip dinged off the post in the 53rd minute.

It’s plays like that Vermes uses to remind Sporting KC that four wins to start the season doesn’t really amount to much. The hard work is still to come.

“There are other things we still need to work on, and I want to guard against thinking that we’re some invincible team,” Vermes said. “By no means have we proven that yet. We’ve made mistakes and there are some things we really need to work on, because if we give a team like LA with Keane or Buddle up top some of the chances that we’ve given away over the course four games, they’re going to punish us. We have to be a lot better in some of those situations.”

Vermes is referring to the Los Angeles Galaxy striker pairing of Robbie Keane, an Irish goal-scoring machine and one of the club’s designated players, and speedy forward Edson Buddle.

Both are world-class finishers and will punish Sporting KC for some of the mistakes the club has heretofore gotten away with.

“Keane and Buddle are probably one of the best tandems in the league right now just with the runs they make and the different challenges they provide to us,” Besler said. “We have to be tuned in and concentrate.”

Vermes did praise the team’s resiliency against FC Dallas after going down a goal in the 25th minute, saying it was similar to the guts shown by a record-setting Wizards defense from 2000 that propelled the club to its only MLS Cup title.

“What I’ve seen this team do over the last five years or so is, when a goal is scored, you could see there was a good chance they weren’t going to come back,” Vermes said. “I don’t think at any moment in that game (against FC Dallas) did our guys feel a lack of confidence to come back into the game.”

Not only did Sporting KC knot the game before halftime, but won on Kei Kamara’s 88th-minute stunner.

“That is something that we had in 2000,” Vermes said. “It was understanding that even when you score, we’re coming right back. There was a confidence and a belief in that. I see these guys having that as well.”